Mozilla Firefox is a graphical web browser developed by the Mozilla Corporation and a large community of external contributors. Firefox started as a fork of the Navigator browser component of the Mozilla Application Suite. Firefox has replaced the Mozilla Suite as the flagship product of the Mozilla project, under the direction of the Mozilla Foundation.

To display web pages, Firefox uses the Gecko layout engine, which implements most current web standards in addition to several features which are intended to anticipate likely additions to the standards. Latest Firefox features include tabbed browsing, spell checking, incremental find, live bookmarking, a download manager, private browsing, location-aware browsing (also known as "geolocation") based exclusively on a Google service and an integrated search system that uses Google by default in most localizations. Functions can be added through add-ons, created by third-party developers, of which there is a wide selection, a feature that has attracted many of Firefox's users. Mozilla Firefox is a cross-platform browser, providing support for various versions of Microsoft Windows, Mac OS X, and Linux.